1. Field of the Invention
The present invention generally relates to a circuit board structure, in particular, to a circuit board structure with heat dissipation effect.
2. Description of Related Art
Recently, with the rapid development of technology, it has an increasingly high requirement on the heat dissipation effect of metal circuit boards of electronic devices. Taking a light emitting diode (LED) for example, the illuminating efficiency of the LED has been gradually enhanced after continuous research and improvement, such that its luminance is further raised to meet more demands from various products. In other words, in order to enhance the luminance of the LED, besides solving the external packaging problem, the LED is also designed to achieve a higher electric power and a higher working current, so as to produce an LED with a higher luminance. However, once the electric power and the working current are raised, the LED generates more heat and easily gets overheated, and thus, the performance of the LED may be deteriorated, and what's worse, a failure may occur.
Currently, most of the metal circuit board structures are made of aluminum, or some others are made of copper. A copper substrate is heavier than an aluminum substrate, but a thermal conductivity of the aluminum substrate is merely half of that of the copper substrate. In order to maintain the advantage of the aluminum substrate of being lighter and to compensate the feature of a lower thermal conductivity than that of the copper, a composite substrate obtained by doping diamond powders in the aluminum substrate has both of the above advantages.
Generally, in order to lay a base layer of circuits on a surface of such a composite substrate, a dielectric layer is disposed between the composite substrate and the circuits for achieving an insulating effect. For example, a dielectric layer with a thickness of only 1 μm (micrometer) to 2 μm is formed on a surface of the composite substrate, and the dielectric layer is, for example, a diamond-like carbon film (DLC film).
However, such a composite substrate is extremely hard, so the rough surface thereof is difficult to be processed or polished. Thus, compared with an ordinary metal circuit substrate, the composite substrate has a higher surface roughness, so that the insulating effect of the coated dielectric layer is weakened. For example, in the circuit board structure provided by the ROC Patent M282455, the insulating effect of the dielectric layer is deteriorated due to the impact of diffusion effects of metal atoms or roughness of the metal composite substrate. Moreover, in the heat sink provided by the ROC Patent I258333, the dielectric layer is mainly used for enhancing the heat dissipation effect, and no solutions about improving the insulating effect are proposed.